Removing Paraquat and Nile blue from aqueous solution using double-oxidized graphene oxide coated by polydopamine nanocomposite

Azo dyes and herbicides are significant environmental contaminants which are characterized by the presence of one or more azo bonds (-N=N-) and aromatic species in their structure. The aim of present work is to use inexpensive and environmentally friendly nanocomposite as an adsorbent. Double-oxidized graphene oxide (GO) sheets are coated by polydopamine to adsorb the studied pollutants Nile blue (NB) and Paraquat (PQ) from wastewater. Characterizations of the synthesized GO coated with polydopamine were investigated by several techniques such as FT-IR, FE-SEM, XRD, adsorption isotherm. The effect of solution initial pH, initial concentration, and contact time was investigated. Results indicate that adsorption capacity in ambient temperature could reach 131.58, 101.01mg/g for Nile blue and Paraquat, respectively. The efficiency of Langmuir isotherm model for these pollutants was acquired from the equilibrium adsorption data. Indeed, based on the experimental results, the possible adsorption mechanism was also suggested.